1. Field of the Invention
The present invention relates to a shaft drive type power transmission, particularly to a shaft drive type power transmission intended to simplify the connection between a propeller shaft and a pinion gear supported by a gear case.
2. Background Art
A prior art connection structure of a shaft drive type power transmission in which a propeller shaft is connected to a pinion gear via a joint xe2x80x9cbxe2x80x9d is shown in FIG. 11. As shown in FIG. 11, a boss xe2x80x9cdxe2x80x9d of a pinion gear xe2x80x9ccxe2x80x9d is splined-connected to one end of the joint xe2x80x9cbxe2x80x9d, and the joint xe2x80x9cbxe2x80x9d is integrated with the pinion gear xe2x80x9ccxe2x80x9d by fastening a nut xe2x80x9cfxe2x80x9d to a thread portion xe2x80x9cexe2x80x9d formed on the boss xe2x80x9cdxe2x80x9d. In this way, the joint xe2x80x9cbxe2x80x9d is sub-assembled with the pinion gear xe2x80x9ccxe2x80x9d on the gear case side. It should be noted that at this connection step, one end of the joint xe2x80x9cbxe2x80x9d is butted to a bearing xe2x80x9chxe2x80x9d for rotatably supporting the pinion gear xe2x80x9ccxe2x80x9d.
A propeller shaft xe2x80x9caxe2x80x9d is then spline-connected to the other end of the joint xe2x80x9cbxe2x80x9d, and one end of a boot xe2x80x9cgxe2x80x9d having the other end previously fixed to the outer periphery of one of the propeller shaft xe2x80x9caxe2x80x9d and the joint xe2x80x9cbxe2x80x9d is fixed to the outer periphery of the other of the propeller shaft xe2x80x9caxe2x80x9d and the joint xe2x80x9cbxe2x80x9d. This type of connection structure has been disclosed, for example, in Japanese Patent Publication No. Sho 63-6399.
FIG. 12 is a view showing a prior art connection structure on the rear wheel side. Like the above connection structure, a joint xe2x80x9cnxe2x80x9d is fixed to a boss xe2x80x9cjxe2x80x9d of a pinion gear xe2x80x9cixe2x80x9d by fastening a nut xe2x80x9ckxe2x80x9d to a threaded portion formed on the boss xe2x80x9cj.xe2x80x9d In FIG. 12, character xe2x80x9cmxe2x80x9d designates a rear end portion of a rear wheel side drive shaft spline-connected to the joint xe2x80x9cnxe2x80x9d, and xe2x80x9cpxe2x80x9d is a spring.
According to the above-described prior art, since the joint xe2x80x9cbxe2x80x9d is sub-assembled with the pinion gear xe2x80x9ccxe2x80x9d on the gear case side by using a nut xe2x80x9cfxe2x80x9d, the boot xe2x80x9cgxe2x80x9d must be mounted, after the propeller shaft xe2x80x9caxe2x80x9d is connected to the joint xe2x80x9cb.xe2x80x9d Since the joint xe2x80x9cbxe2x80x9d is sub-assembled with the pinion gear xe2x80x9ccxe2x80x9d on the connection portion between the propeller shaft xe2x80x9caxe2x80x9d and the joint xe2x80x9cb,xe2x80x9d it is difficult to mount the boot xe2x80x9cgxe2x80x9d on the connection portion between the propeller shaft xe2x80x9caxe2x80x9d and the joint xe2x80x9cbxe2x80x9d. Also, since the joint xe2x80x9cbxe2x80x9d is fixed to the pinion gear xe2x80x9ccxe2x80x9d by using the nut xe2x80x9cfxe2x80x9d, the boss of the pinion gear xe2x80x9ccxe2x80x9d to which the nut xe2x80x9cfxe2x80x9d is to be fastened must be threaded. This inherently increases the number of manufacturing steps and the required number of parts.
The present invention overcomes the shortcomings associated with the prior art and achieves other advantages not realized by the prior art.
Accordingly, it is an object of the present invention to provide a connection between a pinion gear and a propeller drive shaft that is simplified in construction, relatively easily maintained, requires few assembling steps, and ensures solid, reliable connection between mating parts.
It is a further object of the present invention provide a leading end of the joint abutted to a stepped portion of the pinion gear.
It is a further object of the present invention to reduce the requirements of the pinion gear from compensating for axial forces.
These and other objects are accomplished by a shaft drive power transmission for a vehicle in which a propeller drive shaft is connected to a pinion gear on a gear case side of the propeller drive shaft, said transmission comprising a boss of said pinion gear having at least a first diameter portion, a second diameter portion and a third diameter portion, wherein said third diameter portion is larger in diameter than said second diameter portion and said second diameter portion is larger in diameter than said first diameter portion and said first diameter portion is adjacent to said propeller drive shaft; a joint for connecting the pinion gear to the propeller drive shaft, said joint having a shaft end and a pinion end, wherein said shaft end of said joint is operatively spline-connected to said propeller shaft with a spline connection and said pinion end of said joint is operatively spline-connected to said third diameter portion of said boss of said pinion gear with a spline connection and in such a manner as to be integrally connected and rotatable therewith, and wherein the joint is prevented from slipping off of the boss of said pinion gear.
These and other objects are also accomplished by a shaft drive power transmission for a vehicle, said transmission comprising an output shaft transmitting power from a power unit of the vehicle; a front wheel propeller shaft connected to a front end of said output shaft; a right front wheel axle and a left front wheel axle; a front wheel drive case; a pinion gear for distributing drive forces from said front wheel propeller shaft to said right and left front wheel axles; and a boss of said pinion gear having at least a first diameter portion, a second diameter portion and a third diameter portion, wherein said third diameter portion is larger in diameter than said second diameter portion and said second diameter portion is larger in diameter than said first diameter portion; a joint for connecting the pinion gear to the propeller drive shaft, said joint having a shaft end and a pinion end, wherein said shaft end of said joint is operatively spline-connected to said propeller shaft with a spline connection and said pinion end of said joint is operatively spline-connected to said third diameter portion of said boss of said pinion gear with a spline connection and in such a manner as to be integrally connected and rotatable therewith, and wherein the joint is prevented from slipping off of the boss of said pinion gear.
According a first aspect of the present invention, since the joint is fitted to the pinion gear in such a manner as to be integrally rotatable therewith and not to be slipped off therefrom, it is possible to sub-assemble the joint with the propeller shaft, and hence to simplify the assembling process. Further, since it is possible to eliminate the need of fastening the joint to the pinion gear by using a nut as in the prior art structure, it is possible to eliminate the need of threading the boss of the pinion gear and hence to reduce the number of the machining steps and also reduce the number of parts by omitting the nut.
According to a second aspect of the present invention, since the outer periphery of the connection portion between the joint and the propeller shaft is covered with the boot at the step of sub-assembling the joint to the propeller shaft, it is possible to eliminate the need of mounting the boot while connecting the propeller shaft to the pinion gear as in the prior art structure, and hence to omit such a difficult mounting step from the assembly process.
According to a third aspect of the present invention, since the leading end of the joint is abutted to the stepped portion of the pinion gear, the bearing for rotatably supporting the pinion gear can be configured as a common small-sized bearing, thereby resulting in a reduction in the material cost.
According to a fourth aspect of the present invention, since the teeth of the pinion gear are each formed with a straight shape, a reaction force applied upon acceleration/deceleration is, unlike the prior art bevel gear, transmitted not in the axial direction but substantially in the rotational direction. Since the reaction force does not act as a load applied in the axial slip-off direction, it is possible to omit the provision of the nut of the prior art.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.